The main aim of the research project is an understanding of the chemical reactivity of the isoalloxazine ring system of the flavin coenzymes and how this reactivity might be used in biological systems. The method of approach will be to study diverse flavoprotein enzymes in detail, to carry out free flavin model studies, and to integrate the information so obtained in an attempt to answer the fundamental questions which become evident. The four basic questions to which we are seeking answers are: 1) What steps are involved in the reaction of reduced flavins with molecular oxygen, what species of "activated" oxygen are produced and how do they participate in different enzymic reactions? 2) What is the nature and mechanism of flavin catalyzed dehydrogenation reactions? 3) What are the conditions required to obtain charge transfer interactions with flavins and what catalytic significance do such complexes have? 4) What are the electron transfer interactions between flavin and other functional groups in complex enzymes such as xanthine oxidase and aldehyde oxidase?